1. Field of the Invention
The present invention relates to a pulsar ring of a magnetic rotary encoder for detecting a rotation.
2. Description of the Conventional Art
FIG. 4 is a sectional view showing a conventional pulsar ring for a rotary encoder integrally provided in a sealing apparatus 100 for sealing a bearing portion of a wheel suspension apparatus for a motor vehicle by cutting it along a plane passing through an axis O. This kind of sealing apparatus 100 is also called as a hub seal, and is incorporated between end portions of an outer ring 201 and an inner ring 202 of a bearing 200 so as to prevent muddy water or the like from intruding into a bearing inner portion B from a bearing outer portion A.
In particular, the sealing apparatus 100 shown in FIG. 4 is provided with a metal-made mounting ring 101 which is pressure-inserted and fitted to an inner peripheral surface of the outer ring 201 of the bearing 200, and a side lip 102 and a radial lip 103 which are integrally provided in the mounting ring 101, and the side lip 102 and the radial lip 103 are slidably brought into close contact with a slinger 104 tightly fitted to an outer peripheral surface of the inner ring 202. In detail, the side lip 102 and the radial lip 103 are made of a rubber-like elastic material, and are integrally adhered by vulcanization to the mounting ring 101 via a common base portion 102a. The side lip 102 is structured such that a leading end is slidably brought into close contact with an inner side surface of a seal flange portion 104a of the slinger 104, and the radial lip 103 at an inner peripheral side thereof is structured such that an inner peripheral edge of a leading end directed to an outer side is slidably brought into close contact with an outer peripheral surface of a sleeve portion 104b of the slinger 104.
A pulsar ring 105 is integrally provided on an outer side surface of the seal flange portion 104a of the slinger 104, and the pulsar ring 105 is formed by a magnetic rubber made by mixing a magnetic material to a rubber-like elastic material and is magnetized so as to be multipolar at a predetermined pitch in a circumferential direction. Further, a magnetic sensor 120 is arranged at an outer side of the pulsar ring 105 oppositely thereto in a non-rotating state. The magnetic sensor 120 constructs a rotary encoder together with the pulsar ring 105, and is structured such as to generate a pulse having a wave form corresponding to a change of a magnetic field caused by a rotation of the pulsar ring 105 together with the inner ring 202 of the bearing 200 and detect the rotation (refer to Japanese Unexamined Patent Publication No. 2004-93554).
However, conventionally, since the pulsar ring 105 made of the magnetic rubber is provided on the outer side surface of the seal flange portion 104a of the slinger 104, the pulsar ring 105 tends to be exposed to an external disturbance caused by a foreign matter, muddy water, an external magnetic field or the like from the bearing outer portion A. Accordingly, a reduction and a turbulence of magnetic force tend to occur, and it is hard to maintain a stable magnetic pattern.